transactions of the sections. 
87 
On Conjugation in the Diatomaceaa. G. H. K. Tiiwaites, 
b the earlv part of last month (May 2) the author had the good 
ktm examples of Eunoiia turgiila, Ehrenberg, exhibiting m a most satisfactory 
■uerthe process of coningation in its various stages; not long afterwards he dc- 
wriO/ecOBSiut Iflnceo/a/wB, Ebr., Gomphonma minutismmttm. Agardh, and Gow- 
- i [Spkmetla vvlgarit. Kiitziag.x) in the same intcreBtmg condition. 
Iitf theahote-naroed species the process of conjugation w very airmlar, 
character corresponds exactly with what tates place m the Cunjugatex and 
At the conunencenirnt of the process the frnstules are senn to be ap- 
wiioated in pairs, and in eatA pair a corresponding surface of the frustules m more 
T Ik close apposition. After a time each fmstule splits asunder into 
.atheplaoe where fisiiparotis division would ordinarily take place), and ml » • w- 
<t*ie finds egress and combines with that of the opposite frustnle through o 
duwU; thus two distinct ma-sses of mixed eiidochrome are producetl, around eac 
d wich a meaibranc is derelDped, and in this way two sporangia are the result ot 
cinjoeation of a pair of frnstules. . . , _ _ 
Thf iporangia are at first cylindrical and 6 hort,_aad their membrane ext e y 
•ica* j subseqaently however they increase considerably in length, ao as ar 
nwd in dimension tlicr parent frustules, become somewhat fusiftirm. and s ig y 
wved. and with their cell-wall firm and marked with numerous transverse strim : 
mature they beat a very close resemblance to the frustulcs of Cocconcma, 
' -'•'1, ihe sporangia of Coceonma lancpnlntum differ aj)parently in no resjiec s rom 
iW fro!tuJ» of that sriecies, except in their much greater size; nor is there any per- 
»I«ible difference in the character of the endochroine. It seems most probable that 
[‘'lell-wall of the raature sporangium is equally siliceous with that of the frustule, 
Wtthe author had nut heen able to ascertain this point. v v nf 
A coMidcrable quantity of mucus or gelatine is developed around each pair 
'•eMittxl frustulcs and holds them attached to their spurangta. even when tue mtter 
‘Masture, or nearly so. In the Hcvural specie# a difference U observable as to tne 
^iv« position of the mature sporangia to the frustules from which they were pro- 
In £«jiolta tunjida the sporaugia are Bituatcd at right angles to the empty 
fraiiiles, whilst in the other three species above-named they arc parallel to them. 
Errry one familiar with tlie mode of conjugation of the Ihsmiilicx must: perceive, 
foregoing account of this process in the i>fo/om«rfi<e,liow precisely it agrees 
8 erery particular in the two families; and, although in most of the JJcmimefl' only 
• i^oraugium ia produced from the mixed endochrome of a pair of cells, still m 
“*“r two species of C/og«eri»w two sporangia are always developed under similar 
f'fromstam.Qg^ 
question as to the animal or vegetable nature of the Diatomacero may now be 
“onilered settled, for it is surely scarcely possible to refer these interesting produc- 
jl®? to the animal kingdom without aUo including with them the Dosmidiea: and 
'^jugateej, which few naturalists will be disposed to do. 
OnfAe Comparison of the Flora of Britain with that of other countries. 
By Miss Twtking. 
% comparing the flora of our own island with that of the co^****^"^' 
^ view of other part# of the world, a more correct 
number and value of the plants indigenous to ’ otLd to 
our native plants in comicxion xvith , fhev will 
-^^tbey belong, but of which they arc only small and humble 
j^^conaidi-rablc additional interest. Even the Euphorbia, which is .l gf 
weed in gardens, is of the same remarkable S ff 
2?fi«tion and a# worthy of examination as the more ^ighlv ^eloped 
countries acquire u v.aat size and Of 
singular lu tlicir . j 
gS m tribe Legutuinosicwe have several herbaceous specie*, “ 
^luta of a shnibbv nature In nroceeding southwards we hnd Cytisus ami 
trees in this grLp; in 'the Tropics sorfe of the most magnificent flowers 
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